FIELD OF THE INVENTION AND RELATED ART STATEMENT
This invention relates to a tire for an airplane having a sufficient load capacity, being capable of withstanding the centrifugal force generated by high speed revolutions at the time of take-off and landing of the air-plane, and being capable of effective absorption of the shock to which the body of the airplane is subjected.
Recent developments in airplane design have been remarkable and, with the trend toward increases in the weight of the airplane body and in flight speed, stricter requirements for safety in take-off and landing as well as the need for a design capable of dealing with heavy loads and high speeds have become important. The particular requirements of an airplane tire which are different from those for generally used tires incorporate the following characteristics:
(A) The airplane tire is required to absorb the shock which occurs when the airplane lands on the runway, stop the airplane safely, and permit easy take-off; these requirements must be reflected in the design of the tire structure and in the selection of reinforcing materials for the tire. PA1 (B) The airplane tire must be designed such as to have a large degree of flexibility amounting to, for example, 28 to 38 percent, when loaded, for effectively absorbing the shock to which the airplane body is subjected and making take-off and landing safe Accordingly, selection of a tire structure sufficiently resistant to a large degree of repeated deformation and reinforcing materials of suitable quality is necessary. PA1 (C) The weight and size of an airplane tire are limited with a view to reducing a weight of the airplane body as much as possible and, therefore, the relative load per one tire is extremely large. For example, the load on an airplane tire per unit weight thereof under standard atmosphere conditions ranges from 130 to 360 times in the case of times for general use. As regards internal pressure, this may reach as high as 10 to 16 kg/cm.sup.2 in an airplane tire, in contrast to about 8 kg/cm.sup.2 at the maximum in tires for general use. Therefore, an airplane tire needs to be strong enough to withstand such extremely high internal pressures.
An airplane tire must satisfy all of these requirements. However, the tires that have conventionally and broadly been used are of cross-ply structure in which carcass cords are adapted to intersect each other within a ply. Tires of such structure are low in stiffness at the tread part due to the direction in which the carcass cords are arranged and this is undesirable because of poor resistance to wear and of the tendency of generate heat. Further, the tread part bulges at the central portion due to the centrifugal force generated by high speed revolution of the tire and causes enlargement of the tire which is normally temporary but becomes permanent in certain circumstances, and this is far from satisfactory in terms of the durability and life of the, tire. Therefore, the so-called radial structure has come to be used recently which has carcass cords arranged in the radial direction of the tire and which, in addition, is provided with a belt layer composed of highly resilient cord arranged at a comparatively small angle with respect to the direction of the tire circumference on the inner side of the tread for the purpose of increasing the stiffness thereof. This kind of radial tire, however, has a problem in that the shock absorbing effect at the time of take-off and landing of the airplane is inferior because of the arrangement of carcass cords in the radial direction of the tire and also because of the arrangement of highly resilient cords in the belt layer at a small angle with respect to the tire circumference direction. Another problem is that breakage can occur as a result of a large amount of strain at both ends of the belt layer.